AUSTRALIAN winemakers can trick their grapes into maturing later to counteract the effects of climate change, new research shows.
Bud burst: Delayed pruning can slow maturing grapes.
Treasury Wine Estate viticulturist Paul Petrie said the harvest date for Australian wine had come forward by up to 1 1/2 days a year in the past 20 years.
But in a small-scale trial which involved pruning grapevines a month later than usual, Dr Petrie found he could delay the growth of grapes, so they matured later.
"It is just one potential tool to manage the effects of climate change," Dr Petrie said.
Dr Petrie last week presented his findings at the Climate Change Research Strategy for Primary Industries conference in Melbourne.
"Like many wineries, we use a database to manage our harvest decisions and we enter the results of our weekly sugar samples," Dr Petrie said. "We found since 1992 these sugars were accumulating a day or so earlier than they had been."
He also found varieties were starting to ripen closer together.
"There used to be an average of 20 days between two varieties and now there's only nine," he said.
Mr Petrie said this was putting pressure on harvest because it was becoming more compressed, leading to staffing and machinery shortages.
"The aim of the trial was to spread the harvest out again so it's more manageable," Dr Petrie said.
While viticulturists would usually prune from May to August when the trees were dormant, last year Dr Petrie pruned two to three weeks after bud burst when the shoots were 2-3cm long.
"Buds burst at the end of the shoots first, but by pruning the ends of the shoots, the buds closer to the base of the cane burst later."
This translated to a three to four week delay in maturity.
"Delayed pruning is an ideal adaptation option as its implementation costs are very low. "It may actually reduce pruning costs as staff and pruning equipment can be utilised over a longer period," Dr Petrie said.
"It may also improve wine quality, which is something we're waiting to see when we conduct a commercial scale trial on Shiraz this year. It could also help protect against frost."